1. Field of the Invention
The invention relates to a surface treatment method to be performed on a base material, and a coating agent to be applied onto the base material.
2. Description of Related Art
In order to facilitate removal of a cast product from a mold, a surface treatment is performed on the mold (see, e.g., Japanese Patent No. 4868052).
With the technology disclosed in Japanese Patent No. 4868052, fullerene is supplied to a carbon film (amorphous carbon) coating the surface of a mold. Then, the mold is put into a container storing molten metal (e.g., molten aluminum), and the mold is heated. As a result, fullerene is moved into the voids in the carbon film, so that the carbon film is densified, resulting in the reinforcement of the carbon film. The reinforced carbon film is repeatedly cast in the mold, which enables fullerene to penetrate more into the inside (the mold side). Namely, by repeatedly performing casting, it is possible to elongate the life of the mold.
With the technology disposed in Japanese Patent No. 4868052, the carbon film coats the surface of the mold, resulting in an increase in film thickness. In other words, it results that the surface of the mold is coated with a thick carbon film. Further, at the stage before repeatedly performing casting, in other words, at first or second casting, relatively much fullerene may be situated on the surface side of the carbon film. In other words, the mold side of the carbon film may not be sufficiently densified.
Thus, when the carbon film is thick, and the mold side of the carbon film is not sufficiently densified, in first or second casting, the carbon film may be peeled off from the mold.
Herein, to a mold for use, in gravity casting, low pressure die casting, or the like, a coating agent is applied before casting for the purpose of facilitating removal of a product from the mold, or other purposes. As the raw materials for such a coating agent, there are used graphite and the like having good fluidity for molten metal.
The carbon film reinforced by using the technology disclosed in Japanese Patent No. 4868052 is not so good in fluidity for molten aluminum enough to be able to be used in the powder form thereof as the raw material for the coating agent. In other words, the carbon film reinforced by using the technology disclosed in Japanese Patent No. 4868052 cannot be used as the raw material for the coating agent.